JOPSS:検索結果一覧

論文

Polarization dependence of soft X-ray absorption spectroscopy on the heavy fermion superconductor CeNi $_{2}$ Ge $_{2}$

藤原秀紀*; 中谷泰博*; 荒谷秀和*; 金井惟奈*; 山神光平*; 濱本諭*; 木須孝幸*; 関山明*; 田中新*; 海老原孝雄*; et al.

New Physics; Sae Mulli, 73(12), p.1062 - 1066, 2023/12

https://doi.org/10.3938/NPSM.73.1062

We have performed soft X-ray absorption spectroscopy (XAS) on the heavy fermion superconductor CeNi $_{2}$ Ge $_{2}$ to examine the local 4 electronic structure. The XAS spectra are qualitatively explained by ionic calculations, indicating a degree of localized character of the 4 states, while sizable -hybridization effects are also observed in the XAS spectra and those magnetic circular dichroism. In addition, the temperature dependence of linear dichroism in the XAS spectra indicates that the ground state symmetry is $_{7}$ , and the excited states with $_{6}$ symmetry is above 390 K.

論文

Impact of the ground-state 4 symmetry for anisotropic hybridization in the heavy-fermion superconductor CeNi $_{2}$ Ge $_{2}$

藤原秀紀*; 中谷泰博*; 荒谷秀和*; 金井惟奈*; 山神光平*; 濱本諭*; 木須孝幸*; 山崎篤志*; 東谷篤志*; 今田真*; et al.

Physical Review B, 108(16), p.165121_1 - 165121_10, 2023/10

https://doi.org/10.1103/PhysRevB.108.165121

被引用回数：0 パーセンタイル：0(Materials Science, Multidisciplinary)

We report the ground-state symmetry of the Ce 4 states in the heavy-fermion superconductor CeNi $_{2}$ Ge $_{2}$ , yielding anisotropic hybridization between the Ce 4 states and conducting electrons. By analyzing linear dichroism in soft X-ray absorption and core-level hard X-ray photoemission spectra, the 4 symmetry is determined as -type $_{7}$ , promoting predominant hybridization with the conducting electrons originating from the Ge site. The band structures probed by soft X-ray angle-resolved photoemission indicates that the Ge 4 components contribute to the band renormalization through the anisotropic hybridization effects, suggesting that the control of the electronic structures of Ge orbital gives an impact to achieve the exotic phenomena in CeNi $_{2}$ Ge $_{2}$ .

論文

Layer-number-independent two-dimensional ferromagnetism in CrTe

Wang, Y.*; 梶原駿*; 松岡秀樹*; Saika, B. K.*; 山神光平*; 竹田幸治; 和達大樹*; 石坂香子*; 岩佐義宏*; 中野匡規*

Nano Letters, 22(24), p.9964 - 9971, 2022/12

https://doi.org/10.1021/acs.nanolett.2c03532

被引用回数：9 パーセンタイル：83.82(Chemistry, Multidisciplinary)

In a conventional magnetic material, a long-range magnetic order develops in three dimensions, and reducing a layer number weakens its magnetism. Here we demonstrate anomalous layer-number-independent ferromagnetism down to the two-dimensional (2D) limit in a metastable phase of CrTe. We fabricated CrTe thin films by molecular-beam epitaxy and found that CrTe could host two distinct ferromagnetic phases characterized with different Curie temperatures ( $T_mathrm{C}$ ). One is the bulk-like high- $T_mathrm{C}$ phase showing room-temperature ferromagnetism, which is consistent with previous studies. The other is the metastable low- $T_mathrm{C}$ phase with $T_mathrm{C}$ 160 K, which exhibits a layer-number-independent $T_mathrm{C}$ down to the 2D limit in marked contrast with the conventional high- $T_mathrm{C}$ phase, demonstrating a purely 2D nature of its ferromagnetism. Such significant differences between two distinct phases could be attributed to a small variation in the doping level, making this material attractive for future ultracompact spintronics applications with potential gate-tunable room-temperature 2D ferromagnetism.

論文

Enhanced - hybridization intertwined with anomalous ground state formation in the van der Waals itinerant magnet FeGeTe

山神光平*; 藤澤唯太*; Pardo-Almanza, M*; Smith, B. R. M.*; 角田一樹; 竹田幸治; 岡田佳憲*

Physical Review B, 106(4), p.045137_1 - 045137_8, 2022/07

https://doi.org/10.1103/PhysRevB.106.045137

被引用回数：2 パーセンタイル：34.67(Materials Science, Multidisciplinary)

FeGeTe is a van der Waals (vdW) coupled unconventional ferromagnetic metal with a high Curie temperature ( $T_{rm C}$ ), exceeding 300 K. The formation of an anomalous ground state far below $T_{rm C}$ has attracted great interest, leading to a need to understand the spin-polarized electronic state near the Fermi energy ( $E_{rm F}$ ) at low temperature. Despite recent extensive study, a microscopic understanding of the spin polarized electronic structure around $E_{rm F}$ has not been established yet due to the intrinsic complexity of both the crystal and band structures. In this work, we investigate the temperature dependence of element-specific soft X-ray magnetic circular dichroism (XMCD). Systematic temperature evolution in the XMCD signal from both magnetic Fe and its ligand Te is clearly observed. Importantly, the enhancement of the hybridization between Fe 3 and Te 5 states in the zero-magnetic field limit has been revealed. In light of the possible emergence of an exotic ground state, we discuss the temperature and magnetic field evolution of the element specific XMCD results.

論文

Revising the 4 symmetry in CeCu $_{2}$ Ge $_{2}$ ; Soft X-ray absorption and hard X-ray photoemission spectroscopy

荒谷秀和*; 中谷泰博*; 藤原秀紀*; 川田萌樹*; 金井惟奈*; 山神光平*; 藤岡修平*; 濱本諭*; 久我健太郎*; 木須孝幸*; et al.

Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09

AA2018-0352.pdf:1.16MB

https://doi.org/10.1103/PhysRevB.98.121113

被引用回数：5 パーセンタイル：25.82(Materials Science, Multidisciplinary)

We present a detailed study on the ground state symmetry of the pressure-induced superconductor CeCuGe probed by soft X-ray absorption and hard X-ray photoemission spectroscopy. The revised Ce ground states are determined as $|{Gamma_7}rangle=sqrt{0.45}|{J_{z}=pm frac{5}{2}}rangle - sqrt{0.55}|{mp frac{3}{2}}rangle$ with in-plane rotational symmetry. This gives an in-plane magnetic moment consistent with the antiferromagnetic moment as reported in neutron measurements. Since the in-plane symmetry is the same as that for the superconductor CeCuSi, we propose that the charge distribution along the -axis plays an essential role in driving the system into a superconducting phase.

論文

Three-dimensional electronic structures and the metal-insulator transition in Ruddlesden-Popper iridates

山崎篤志*; 藤原秀紀*; 橘祥一*; 岩崎大昌*; 東野勇志*; 吉見千秋*; 中川広野*; 中谷泰博*; 山神光平*; 荒谷秀和*; et al.

Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11

AA2016-0587.pdf:2.55MB

https://doi.org/10.1103/PhysRevB.94.115103

被引用回数：17 パーセンタイル：61.21(Materials Science, Multidisciplinary)

軟X線角度分解光電子分光を用いて、Ruddlesden-Popper型イリジウム酸化物Sr $_{n+1}$ Ir $_{n}$ O $_{3n+1}$ の3次元バンド構造を調べた。その結果、IrO $_{2}$ 面構造の次元性の増加と共に発現する金属-絶縁体転移に関する直接的な証拠を得た。この転移は、スピンー軌道結合により生じた $j_{eff}$ = 1/2バンドがフェルミエネルギーを横切ることにより生じる。入射光エネルギーを350eV以上走査することにより、SrIrO $_{3}$ の3次元フェルミ面形状及び、Sr $_{3}$ Ir $_{2}$ O $_{7}$ の $k_{z}$ 依存した光電子強度の振動を明らかにした。本手法は、電子状態の全体像の理解において非常に有効である。

論文

Thickness-dependent magnetic properties and strain-induced orbital magnetic moment in SrRuO $_{3}$ thin films

石上啓介*; 吉松公平*; 豊田大介*; 滝沢優*; 吉田鉄平*; 芝田悟朗*; 原野貴幸*; 高橋文雄*; 門野利治*; Verma, V. K.*; et al.

Physical Review B, 92(6), p.064402_1 - 064402_5, 2015/08

https://doi.org/10.1103/PhysRevB.92.064402

被引用回数：45 パーセンタイル：84.02(Materials Science, Multidisciplinary)

Thin films of the ferromagnetic metal SrRuO $_{2}$ (SRO) show a varying easy magnetization axis depending on the epitaxial strain, and undergo a metal-to-insulator transition with decreasing film thickness. We have investigated the magnetic properties of SRO thin films with varying thicknesses fabricated on SrTiO $_{3}$ (001) substrates by soft X-ray magnetic circular dichroism at the Ru M2,3 edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to nonmagnetic at around 3 monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be 0.1B/Ru, and remained nearly unchanged with decreasing film thickness while the spin magnetic moment decreases. A mechanism for the formation of the orbital magnetic moment is discussed based on the electronic structure of the compressively strained SRO film.

論文

Probing strongly correlated 4-orbital symmetry of the ground state in Yb compounds by linear dichroism in core-level photoemission

森健雄*; 北山賢*; 金井惟奈*; 内免翔*; 藤原秀紀*; 東谷篤志*; 玉作賢治*; 田中新*; 寺嶋健成*; 今田真*; et al.

Journal of the Physical Society of Japan, 83(12), p.123702_1 - 123702_5, 2014/12

https://doi.org/10.7566/JPSJ.83.123702

被引用回数：16 パーセンタイル：68.53(Physics, Multidisciplinary)

正方晶YbRh $_{2}$ Si $_{2}$ 及びYbCu $_{2}$ Si $_{2}$ に対して、角度分解内殻光電子分光における直線偏光線二色性を発見し、それにより、基底状態の強相関4軌道の対称性を明らかにした。理論計算から、この線二色性は結晶場効果に由来する異方的な電荷分布を反映することが示された。結晶場の第一励起エネルギーよりもはるかに低温での測定により、両物質の基底状態の4波動関数の決定に成功した。更に、温度依存性測定により、励起状態の対称性についても調べた。

論文

Thickness-dependent ferromagnetic metal to paramagnetic insulator transition in La $_{0.6}$ Sr $_{0.4}$ MnO thin films studied by X-ray magnetic circular dichroism

芝田悟朗*; 吉松公平*; 坂井延寿*; Singh, V. R.*; Verma, V.*; 石上啓介*; 原野貴幸*; 門野利治*; 竹田幸治; 岡根哲夫; et al.

Physical Review B, 89(23), p.235123_1 - 235123_5, 2014/06

AA2015-0419.pdf:0.33MB

https://doi.org/10.1103/PhysRevB.89.235123

被引用回数：23 パーセンタイル：66.6(Materials Science, Multidisciplinary)

Metallic transition-metal oxides undergo a metal-to-insulator transition (MIT) as the film thickness decreases across a critical thickness of several monolayers (MLs), but its driving mechanism remains controversial. We have studied the thickness-dependent MIT of the ferromagnetic metal La $_{0.6}$ Sr $_{0.4}$ MnO by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. The results suggest that the ferromagnetic phase gradually and most likely inhomogeneously turns into the paramagnetic phase and both phases abruptly become insulating at the critical thickness.

発表形式

掲載資料名

発表会議名

筆頭著者名

キーワード

使用言語

発行年

開催年